Comparative evaluation of apically extruded debris with V-Taper, ProTaper Next, and the Self-adjusting File systems.

BACKGROUND: Complete cleaning of the root canal is the goal for ensuring success in endodontics. Removal of debris plays an important role in achieving this goal. In spite of advancements in instrument design, apical extrusion of debris remains a source of inflammation in the periradicular region. AIM: To comparatively evaluate the amount of apically extruded debris with V-Taper, ProTaper Next, and the self-adjusting File (SAF) system.
MATERIALS AND METHODS: Sixty-four extracted human mandibular teeth with straight root canals were taken. Access openings were done and working length determined. The samples were randomly divided into three groups: Group I - V-Taper files (n = 20), Group II - ProTaper Next (n = 20), Group III - SAF (n = 20). Biomechanical preparation was completed and the debris collected in vials to be quantitatively determined. The data obtained was statistically analyzed using ANOVA and post hoc Tukey's test.
RESULTS: All the specimens showed apical debris extrusion. SAF showed significantly less debris extrusion compared to V-Taper and ProTaper Next (P < 0.001). Among Groups I and II, ProTaper Next showed lesser debris extrusion as compared to V-Taper, but it was not significant (P = 0.124).
CONCLUSION: The SAF showed least amount of apical debris extrusion when compared to newer rotary endodontic instruments. This indicates that the incidence of inter-treatment flare-ups due to debris extrusion would be less with the SAF.

INTRODUCTION

Biomechanical preparation is one of the most important stages in endodontic treatment. For a successful outcome, vital and necrotic tissues, microbes, and dentin debris should be removed from the canal system.[12] However, these materials may be extruded through the apical foramen into the periapical tissues during the canal preparation.[3] In asymptomatic chronic peri-radicular lesions due to infected canals, there is always a balance between the microbial toxic effect from the infected canal and the host defenses. During the canal preparation, if the bacteria are extruded apically, there will be an acute inflammatory response from the host due to the increased number of bacterial irritants.[4]

On comparing the apical debris extrusion between hand and nickel-titanium (NiTi) instrumentation, Reddy and Hicks[5] suggested various factors which account for the increased apical extrusion of debris. They include canal preparation up to the apex and type of canal preparation,[6] the diameter of the apical preparation,[7] amount and method of delivery of irrigant,[8] and formation of dentin plug.[9]

ProTaper Next (DENTSPLY Tulsa Dental Specialties, Tulsa, USA) with an M-Wire NiTi configuration has an asymmetric rectangular cross-section with its axis differing from its center of mass. This ensures only two-point contact with the canal wall at a time. This results in increased strength and reduced lateral and apical compaction of debris with more efficient cleaning of the canal.

The variable taper rotary files (SS White, Philadelphia, USA) developed by Dr. Charles Goodis, allows attainment of deeper apical shape with fewer instruments. It has a parabolic cross-section, and it uses Endonol, a special type of NiTi alloy made by advanced metallurgical techniques.

The Self-adjusting File (SAF) (ReDent Nova, Ranaana, Israel) is a novel instrument consisting of a hollow NiTi file composed of a lightly abrasive metal lattice that allows for dentin removal with a back and forth grinding motion. The metal lattice is claimed to adapt itself intimately to the canal walls. Histopathological evaluation has shown the SAF system improved the debridement quality in oval-shaped canals.[10] The continuous flow of sodium hypochlorite along with the grinding motion makes an assumption that the amount of extruded debris will be minimal.[10]

This study aims at estimating the amount of apically extruded debris with ProTaper Next, V-Taper, and the SAF system and evaluating their efficiency in minimizing the amount of apical debris extrusion during use. Null hypothesis considered was that all the systems had the same amount of apical debris extrusion.

MATERIALS AND METHODS

Sixty-four freshly extracted human mandibular premolars with straight single root canals with <5° curvature measured according to Schneider method[11] were collected. All the teeth were analyzed again radiographically to verify in bucco-lingual and mesio-distal aspect for confirmation of single straight canal, complex anatomy, calcifications, and mature apex formation.

Single orifices were further verified by viewing the apices under dental operating microscope (Moeller Wedell, Germany) under ×16 magnification. The root surfaces were cleaned of debris and tissue with periodontal curette. Buccal cusp tips were ground to ensure a flat coronal reference point and a total tooth length of 18 mm. Coronal access entry was prepared with high-speed bur, and all the canals were checked for apical patency with a K-File (015/02) (Mani, Japan). Working length (WL) was obtained by measuring the length of the initial instrument (015/02 K-File) at apical foramen minus 1 mm. The samples were divided randomly into three groups according to the file system used for the preparation of root canals.

In this study, an experimental model described by Myers and Montgomery[6] was used. Stoppers were separated from Eppendorf tubes (Eppendorf India Ltd., Chennai, India) and an analytical balance (Shimadzu Corp. S.P.M. Inc., Philippines) with an accuracy of 10−4 g was used to measure initial weight of the tubes. Three consecutive weights were obtained for each tube and mean calculated. A hole was created in each stopper and tooth inserted up to cementoenamel junction and sealed with cyanoacrylate resin. A 24-gauge needle was placed alongside the stopper to balance the pressure inside and outside the tubes. To avoid variation and eliminate bias, the tubes were covered with foil and the cleaning, shaping and irrigation of all samples was completed by single operator. The assessment of debris extrusion was performed by the second examiner who was blinded with respect to assorted groups.

Group I: V-Taper

Coronal shaping was done using 025/08. Glide path was established using K Hand Files (015/02). Apical shaping was done using 020/06 with X-Smart endodontic motor (Dentsply Maillefer, Ballaigues, Switzerland) according to manufacturer's recommendations to the WL. The final preparation was done till 025/08. Total quantity of irrigant used was 20 ml of distilled water.

Group II: ProTaper Next

Coronal third was prepared using ProTaper Universal Sx in brushing manner and glide path was established using K-File (015/02). Apical preparation was done with X1 (017/04) sequentially followed by X2 (025/06) till WL. 5 ml of distilled water was used after each file, and total quantity of 20 ml distilled water was used.

Group III: Self-adjusting File system

Glide path was established using K-File (015/02) followed by K-File (020/02) to the WL as instructed by manufacturers. Then the SAF (2.0 mm diameter, 21 mm length) was used in canal using RDT3 Nx handpiece head (Re Dent Nova, Ra'naana, Israel) that produced 5000 vibrations per minute with 0.4 mm of amplitude. SAF was used for 4 min with distilled water irrigation at flow rate of 5 ml/min. Total irrigant used was 20 ml.

After instrumentation was complete, the stopper assembly was removed from Eppendorf tube and debris adhered to root surface was collected by washing the root surface with 1 ml of distilled water. Tubes were incubated at 70°C for 5 days to evaporate the distilled water. Second weighing was done by another examiner who was blinded to the various samples. Eppendorf tubes were weighed using the same analytical balance to obtain final weight of tubes including extruded debris. Three consecutive weights were established and mean calculated. Dry weight of extruded debris was calculated by subtracting the weight of empty tube from that of the tube containing debris.

The results obtained were subjected to statistical analysis using ANOVA and post hoc Tukey's test.

RESULTS

After obtaining the values, mean and standard deviation was calculated and subsequently subjected to ANOVA (P < 0.001). There was a significant difference of the debris extrusion in the three instrumentation techniques. To obtain the comparison between the groups, the results were subjected to post hoc Tukey's test in which SAF showed a significant reduction in debris extrusion when compared with ProTaper Next and V-Taper (P < 0.001). When comparing ProTaper Next and V-Taper, there was reduced debris extrusion with ProTaper Next as compared to V-Taper, but the difference was not statistically significant (P = 0.124) [Table 1].

Table 1

Mean debris extrusion and standard deviation

DISCUSSION

Flare-ups are a common problem that clinicians encounter during root canal treatment. One of the common reasons cited for such an incidence is the extrusion of debris present within the canal and also created during the instrumentation of the root canal system into the periradicular region, resulting in an acute periapical inflammation. This may manifest as severe pain which in some cases may be accompanied by swelling. There are many factors which contribute to apical debris extrusion. Irrigation of the root canal space, necrotic pulps, depth of file insertion into the canal, technique of biomechanical preparation, amount of coronal and middle third flaring, and adjunctive irrigation aids have a role in deciding the amount of apical debris extrusion.

The current concept is that the crown-down technique extrudes less debris apically than the step-back technique[12] and a rasping up-down motion of the file extrudes more debris when compared to instruments used in rotational motion.[6] The use of rotary NiTi instruments in root canal preparation has become the norm. More recently, advanced instrument designs including noncutting tips, radial lands, different cross-sections, and varying tapers have been developed to improve working efficiency and safety.

In this study, a single operator prepared all the canals. A standardized protocol given by Fairbourn et al.,[13] was followed to decrease the number of variables involved. Teeth used in this study were selected to have a single canal and foramina and a closed mature apex. To obtain a fixed, reliable reference point, the teeth were decoronated with standard length of 18 mm. The amount of irrigant used in all the three techniques was kept constant at 20 ml. Considering the need for accurate measurement, pure distilled water was chosen to reduce the chance of any particulate matter affecting the results. Sodium hypochlorite has the disadvantage of crystallization in the collection tube which affects the measurement of debris collection.

The protocol suggested by Myers and Montgomery is an in vitro method which does not take into account the periapical tissue resistance while preparing the canal. In clinical situations, the periapical tissues act as a natural barrier to the extrusion of debris apically. The width of the apical constriction may affect the amount of apically extruded debris. Tinaz et al.[7] reported that increase in the diameter of the apical preparation increases the amount of debris extrusion. To standardize the samples, teeth with an apical width size of 0.15 mm were selected in this study.

In this study, SAF showed statistically significant reduction in amount of extruded debris when compared with V-Taper and ProTaper Next. This could be due to the fact that the metal part of the file has an up-down motion while being closely adapted to the canal wall. This feature, coupled with the continuous irrigation through the hollow core and activation of the irrigant by its vibratory motion could have contributed to the excellent result. ProTaper Next had lesser debris extrusion as compared to V-Taper, but it was not significant.

There have been various studies showing the efficacy of SAF in reducing the amount of apical debris extrusion. It has been compared with ProTaper Universal, ProTaper Next, and WaveOne,[1415] with Reciproc[16] wherein the findings of our study are in agreement.

CONCLUSION

All instrumentation techniques resulted in apical debris extrusion. In this in vitro study, due to the absence of the back pressure provided by the periapical tissues, there could have been variation in debris extrusion with these techniques. This point should be kept in mind when the findings of this study are applied in a clinical scenario. Considering these limitations, the SAF had significantly lesser apical debris extrusion when compared to ProTaper Next and V-Taper files. ProTaper Next had lesser amount of debris extrusion as compared to V-Taper files.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest